Thin-walled containers and thin-walled closures for containers



April 7, 1964 J. G. SHERLOCK 3,128,005

THIN-WALLED CONTAINERS AND THIN-WALLED CLOSURES FOR CONTAINERS FiledAug. 4, 1961 2 Sheets-Sheet 1 JOHN G. SHERLOCK ATTORNEY April 7, 1964 J.G. SHERLOCK 3,123,005

THIN-WALLED CONTAINERS AND THIN-WALLED CLOSURES FOR CONTAINERS FiledAug. 4, 1961 2 Sheets-Sheet 2 INVENTOR JOHN G. SHERLOCK United StatesPatent 3,128,005 THIN-WALLED CONTAINERS AND THW-WALLEB CLGSURES FORCONTAINERS John Gerrard Sherlock, Feltham, England, assignor toContinental Can Company, Inc., New York, N.Y., a corporation of New YorkFiled Aug. 4, 1961, Ser. No. 129,318 Claims priority, appiication GreatBritain Aug. 5, 1960 5 Ciairns. ((Zl. 229-39) This invention relates tothin-walled containers and thin-walled closures for containers, referredto generically as container means, made of resilient sheet material suchas polystyrene by moulding, and has for its object to provide acontainer and/ or a closure for a container having a tubular partthereof formed with a screwthread for screwthreaded engagement with acooperating part so that a container can be closed by a closure havingscrewthreaded engagement therewith, in which the appropriate tubularpart of the container and/or closure can have the screwthread formedthereon in the moulding process, e.g. by expansion into a mould underthe action of pressure and/ or vacuum while in a soft condition, whileyet enabling the container or closure after moulding to be removed fromthe mould without the necessity for rotating it relatively to the mouldto unscrew the screwthreaded part thereof from the part of the mould inwhich the screwthreaded part is formed.

Thus, an object of the invention is to enable containers and/ orclosures for containers of the screwthreaded type to be formed bymoulding, for example in batches from a piece of sheet material byexpansion into moulds under air pressure, with or without initialexpansion by mechanical means, followed by bodily removal of thearticles thus formed from the moulds either still attached to theremainder of the sheet material or not, in the same general way as ifthe articles were of a form not provided with a screwthread.

In a thin-walled container or a thin-walled closure for a container madeof resilient sheet material according to the present invention, thecontainer or the closure includes a thin-walled tubular part having ascrewthread of the reverse buttress type formed thereon by deformationof the material without substantial change in its thickness, the tubularpart on which the screwthread is formed being of mean tapered form withthe narrow flank of the reverse buttress thread facing towards thesmaller end of the tubular part While the angle of the mean taper issuch in relation to the axial length of the wider flank of the reversebuttress thread, the angle which this wider flank makes with the axis ofthe tubular part, and the mean taper of such tubular part, that, incross-sections containing the axis of the tubular part, whereas thewider flank of the thread is inclined at a small angle to the said axisin one sense, the line representing the mean taper of the tubular partis inclined at a slightly larger angle to the said axis in the oppositesense and so that, as regards any two adjacent convolutions of thethread the crown of the convolution lying nearer the smaller end of thetubular part lies nearer to said axis than the root of the convolutionlying nearer the larger end of the tubular part.

By the expression a screwthread of the reverse buttress type is to beunderstood a screwthread of which one flank has a relatively long axiallength and lies at a small angle to the axis of the thread while theother flank has a negligible or relatively short axial length and liesat a relatively large angle to the axis of the thread, the relativelylong flank being that which in use takes the axial thrust of thecooperating screwthreaded part, as opposed to a buttress thread in whichthe short flank takes such axial thrust.

By a thread formed by deformation of the material without substantialchange in its thickness is to be understood a thread formed as a helicalcorrugation in the material so that the thread form appears on both theoutside and the inside of the tubular part, although the thread underconsideration will in each instance be only that appearing either on theoutside or the inside of the tubular part, depending on whether thispart constitutes or is arranged to constitute respectively a male orfemale threaded part. Thus, references to the screwthread herein are tobe understood as referring to the thread form which is on that surfaceof the tubular part which in use cooperates with a cooperating threadform to form a screw connection between a container and a closure.

The construction is such that the screwthread can be formed by mouldingand, following such moulding, the article and the mould can be separatedby axial displacement without relative rotation, due to the fact thatthe resilience of the material coupled with the small angle which thewider flank makes with the axis of the tubular part allows eachconvolution of the thread to be withdrawn axially from the cooperatingconvolution on the mould while moreover after such withdrawal eachconvolution, having been separated from the convolution on the mouldwith which it originally made contact, can be moved clear of the diewith little or no further contact with any of the other convolutions onthe mould past which it then travels.

When the invention is applied to a container the screwthread might beformed within the bore of the open end of the container, in which casethe container would preferably have an annular surface area adjacent toits end arranged to make sealing contact with a corresponding surfacearea on a flange or the like on an externally screwthreaded closure.

Preferably, however, in a container according to the invention thescrewthreaded tubular part is in the form of a tubular collar or flangeformed integral with the open end of the container and extending fromsuch open end in the same direction as the body of the container so asto lie around and be spaced from the open end of the body portion of thecontainer. In this case the screwthreaded part would be engaged by acorresponding screwthreaded part of an axially extending flange of acap-like closure member and the cap-like closure would then preferablyhave a smooth externally tapered annular rib formed on its inner faceand arranged to cooperate and make a sealing joint with a correspondingformation immediately within the open end of the container. Thus, thecooperating screwthreaded parts would serve to draw the rib into closesealing contact with the interior of the open end of the container.

In such a construction it would be understood that the screwthread onthe flange of the closure member would conveniently also be formed in asimilar manner to the screwthread on the container so that the closuremember would itself also be in accordance with the invention.

Thus a preferred form of the invention would comprise a container and acooperating closure member both according to the invention.

Containers and/or closure members according to the invention wouldconveniently be made of a thin resilient plastic material such aspolystyrene or polyvinyl chloride and where :a container and acooperating closure member, both according to the invention, areprovided, different materials may be used for the two parts, forexample, for the purpose of preventing or reducing binding of the lid onthe container. In any event, the parts are conveniently formed bymoulding in a manner generally known per se fromv a sheet of appropriateplastic material which, when in a soft deformable state, is disposedover one or more mould cavities or in contact with the end of a suitabledie and then drawn or pressed into close contact with the surfiaces ofsuch cavities or such die by the application of fluid pressure auid/ orvacuum, with or without an initial mechanical deformation of thematerial into the cavities or over the die before the application ofsuch pressure or vacuum.

One example or a container and of a suitable cooperating closure, bothaccording to the invention, is shown the accompanying drawings, in whichFIGURE 1 is as to the lefthand half a cross-section on an enlarged scalecontaining the axis of the container, and as to the righthand half aside elevation on the sarne scale,

FIGURE 2 is a similar view to FIGURE 1 of the closure, the closure andcontainer being shown as slightly separated from one another inreadiness for application of the closure to the container, and

FIGURE 3 is a plan view of the closure member shown in FIGURE 2.

In the construction shown in the accompanying drawings, the containermay be assumed to have a mean diameter of about 2 /2 inches and be madeof polystyrene of a thickness of approximately .012". It comprises abody part 1 of somewhat tapered tubular tform closed at its lower end byan integral bottom wall 2 while its upper edge portion is turned over asshown to provide a tubular part 3 which is formed in the mouldingprocess with a male screwthread of the reverse buttress type. Thetubular turned-over edge portion 3 in which the screwthread is formed isof mean tapered form and the thread formed so that the narrow flank 4 ofthe thread faces towards the larger end of the aubular part 3. The angleof the mean taper is, as shown, approximately 8", while the engle whichthe wider flank 5 of the buttress thread makes with the axis of thetubular part 3 is 6. Moreover, the angles in question are such inrelation to the axial length of the wider flank 5 of the reversebuttress thread that, as regards any two adjacent convolutions of thethread, eg. 6,

the crown of the convolution lying nearer the smaller end of the tubularpart 3 lies nearer to the axis of the tubular part than does the root,e.g. 7, of the convolution lying nearer the larger end of the tubularpart 3.

The axial length of the Wider flank in the example shown may be assumedto be that which will provide seven threads per inch while the radialdepth of the narrow flank is approximately .002".

The construction shown is such that the screwthread can be formed bymoulding, and so that following such moulding the container and themould can be separated by axial displacement without relative rotationdue to the fact that the resilience of the material, coupled with thesmall angle which the Wider flank 5 makes with the axis of the tubularpart, allows the convolutions of the thread to be Withdrawn axially fromthe cooperating convolution on the mould, while moreover, aiter eachconvolution has by such withdrawal been separated from the convolutionon the mould with which it originally made contact, it can be movedclear of the die with little or no further contact with any of the otherconvolutioos on the mould past which it then travels. The upper end ofthe con tainer is formed to provide a short firusto-conical internalsurface 8 to provide substantially sealing contact with a correspondingsurface on the closure as hereinatter described.

The closure comprises a disc-like part 9 anannular portion of whichadjacent to its circumferential edge is formed with a downwardlyprojecting annular rib-like part 10 providing a conical surface to makesealing engagement with the surface 8 of the container referred toabove. Depending from the extreme circumferential edge ct the disc-likepart is a tubular flange 11 formed with a female sorewthread of thereverse buttress type similar in form to the screwthread on thecontainer. Thus this tubular part is formed with a screwthread of meantapered form, the angle of taper being 8 while the wider flank 12 of thereverse buttress screwthr'ead makes an angle with the axis of thescrewthread of approximately 6. As shown, the larger diameter end of theWider flank 12 adjacent to the smaller diameter end of the tubular part11 as a whole.

The dimensions of the closure are such that when it is screwed on to thecontainer, the tapered surface 8 and the part 10 come intocloseengagcment approximately at the moment when during thescrewing-down the screw-threads respectively :on the closure member andcontainer grip one another over substantially their whole areas due tothe 8 mean taper of the parts 3 and 11.

The container is provided with a circumferential rib 13 which when onecontainer is nested in another similar container engages the surface 8and thus prevents the containers jamming one the other, while theclosure is provided with three downward projections 14 adjacent to itscircumference similarly to prevent similar closure members jamming inone another when nested together, and with a ring of serrations as shownat 15.

In a typical example while the container is made of polystyrene theclosure member might be made of a hard polyvinyl chloride.

What I claim as my invention and desire to secure by Letters Patent is:

1. A thin-walled container means made of resilient plastic sheetmaterial, including a thin-walled tubular part having a screwthread ofreverse buttress type formed thereon by deformation of the materialwithout substantial change in its thickness, the tubular part on whichthe screwthread is formed being of mean tapered form and with the narrowflank of the reverse buttress thread facing towards the smaller end ofthe tubular part, while the angle of the mean taper is such in relationto the axial length of the wider flank of the reverse buttress thread,the angle which this wider flank makes with the axis of the tubular partand the mean taper of such tubular part that, in cross-sectionscontaining the axis of the tubular part, whereas the wider flank of thethread is inclined at a small angle to the said axis in one sense, theline representing the mean taper on the tubular part is inclined at aslightly larger angle to the said axis in the opposite sense and sothat, as regards any two adjacent convolutions of the thread, the crownof the convolution lying nearer the smaller end of the tubular part liesnearer to said axis than the root of the convolution lying nearer thelarger end of the tubular part.

2. A container means as claimed in claim 1 in which the tubularscrewthreaded part of the container means is in the form of a collar orflange which extends tirom the open end of the container means in thesame direction as the body of the container means so as to lie aroundand be spaced from the open end of the body portion of the containermeans.

3. A container means as claimed in claim 2 including an approximatelyfrusto-conical surface formed within the end part of the container meansfrom which the screwthreaded tubular part extends, such surfiace beingprovided to form a seal with a cooperating surface on a second containermeans.

4. The combination of two container means as claimed in claim 1, incooperation wherein the screwthreaded tubular parts of said containermeans are formed to engage one another.

5. A container means as defined in claim 3 compris ing a closure havingan annular rib having a surface arranged to cooperate with thefrusto-conicall surface on said container means (to form a substantiallyfluid-tight seal when the closure is fully screwed on to the containermeans.

References Cited in the file of this patent UNITED STATES PATENTSPend'leton Sept. 28, 1897 Campbell Aug. 13, 1912 McLain Oct. 3, 1922Nutter May 13, 1958 Aldington Jan. 26, 1960 Williamson Oct. 24, 1961

1. A THIN-WALLED CONTAINER MEANS MADE OF RESILIENT PLASTIC SHEETMATERIAL, INCLUDING A THIN-WALLED TUBULAR PART HAVING A SCREWTHREAD OF"REVERSE BUTTRESS" TYPE FORMED THEREON BY DEFORMATION OF THE MATERIALWITHOUT SUBSTANTIAL CHANGE IN ITS THICKNESS, THE TUBULAR PART ON WHICHTHE SCREWTHREAD IS FORMED BEING OF MEAN TAPERED FORM AND WITH THE NARROWFLANK OF THE REVERSE BUTTRESS THREAD FACING TOWARDS THE SMALLER END OFTHE TUBULAR PART, WHILE THE ANGLE OF THE MEAN TAPER IS SUCH IN RELATIONTO THE AXIAL LENGTH OF THE WIDER FLANK OF THE REVERSE BUTTRESS THREAD,THE ANGLE WHICH THIS WIDER FLANK MAKES WITH THE AXIS OF THE TUBULAR PARTAND THE MEAN TAPER OF SUCH TUBULAR PART THAT, IN CROSS-SECTIONSCONTAINING THE AXIS OF THE TUBULAR PART, WHEREAS THE WIDER FLANK OF THETHREAD IS INCLINED AT A SMALL ANGLE TO THE SAID AXIS IN ONE SENSE, THELINE REPRESENTING THE MEAN TAPER ON THE TUBULAR PART IS INCLINED AT ASLIGHTLY LARGER ANGLE TO THE SAID AXIS IN THE OPPOSITE SENSE AND SOTHAT, AS REGARDS ANY TWO ADJACENT CONVOLUTIONS OF THE THREAD, THE CROWNOF THE CONVOLUTION LYING NEARER THE SMALLER END OF THE TUBULAR PART LIESNEARER TO SAID AXIS THAN THE ROOT OF THE CONVOLUTION LYING NEARER THELARGER END OF THE TUBULAR PART.